Process of preparing etching-grounds.



J. BAKER.

\\ PROCESS 0F PREPARING ETCHING GROUNDS.

(Application led Nov. 15, 1897.)

Patented July 3|, |900.

(No Model.)

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UNrIeD STATES VPAJIENT OFF-rent JoHN BAKER, oF'BIRMINeHAM, ENGLAND.

PROCESS OF PREPARING ETCHlNG-GROUNDS.

SPECIFICATION forming part of Letters Patent No. 654,867, dated July 31, 1900.

Application iiledNovemher'l, 1897. Serial No,658,620. (Nospeolmens.)

una

T0 @ZZ whom it muy con/cerro:

Be it known that I, JOHN BAKER, a subject of the Queen of England, residing at Birl min gham,England,have invented certain new and useful Improvements in Processes of Preparing Etching-Grounds, (for whichI `have obtained Letters Patent in England,No. 6,924, dated April 4, 1895; in' France, No.` 251,042,v

dated October 21, 1895, and in Germany, No. 93,392, dated October 22, 1895,) of which the following is a specification.

This invention relates *tof etching-grounds ter corresponding in shape with that of the' upstanding type or design upon the form or block. After the transference to a metal surface of a perforated etching-ground thus produced the metallic surface protected bythe etching-ground, except where portions of the latter have been removed, is immersed in the usual acid bath or solution of a metallic salt, and in afew minutes the surface will be found etched to a depth corresponding to the strength of the bath employed and deeply enough for printing from in the ordinary manner. Instead of eecting the removal of portions of the etching-ground by impression they may be removed with the aid'ofa needle or equivalent hand-tool. As the face of the ground upon which the artist works can in transferring the ground to the plate be placed in contact with the latter, so as to become the back, it is not necessary that the artist should primarily work'in reverse by making the righthand side of his picture that which is to be the left-hand side in a print from the design etching, or vice versa,

According to my inventionI obtain a transferable etching-groundby placing or forming an etching-ground of an acid-resisting medium upon a layer of material hereinafter termed a basis, which ordinarily retains the etching-ground securely, but is readily separable therefrom when desired, either by ,being pulled away from it or by being dissolved while the etching-ground remains nnaected. The acid-resisting medium should preferably be such that it can be spread upon the basis in a liquid or viscous state and that `it will `thereafter dry quickly and completely and become firmly adherent to the basis or to an adhesive facing provided on the latter, or it maybe ofsucha nature that it can be made into a block or mass from which When it is `dry thin films can be shaved, each of which :will stick firmly to the basis or to the adhesive-facing of the basis when pressed thereupon, or it may be prepared as a solution vter described,and yet it should not spread under the influence of moderate heat or when pre'ssure is applied to the back of its basis in the operation of transferring, nor must it fail` when transferred to adhere closely to the metal plate which is to be etched. The acid-f resisting medium above referred to can be made by dissolving most kinds of lithographie transfer writing-ink in turpentine, benzin, or `other solvent and then spreading the solution upon' any of the bases hereinafter described by means of a printers composition roller, allowing the solvent time to evaporate before the grounds are used for etching. The addition of a little printing-ink--say about iive per cent. of the weight of the lithographie ink aforesaid-to the dissolved writing transfer-ink facilitates the distribution of the solution; but it must be used sparingly. An ink suited for use as an acid-resisting medium can be made by mixing .togetherwith the aid of heat two and one-half parts of beeswax, one-half part of Pears soap, one part of Mander Brothers medium varnish, one part of Brunswick black; adding to the ,mass While in a warm state` five parts of spirits of turpentine, these parts being by Weight.

IOO

loe capable of being` peeled oif or otherwise parted from the ground after being moistened lon the back and may be, for instance, lithographers transfer-paper well coated with the coating compositions ordinarily used-such" as iiour or starch-paste, gum, ordextrine,Y with or without treacle. 1f thebasis is to be, soluble, it may be composed, for instance, of a very thin lm of gelatin, with or without the addition of dextrine or of saccharine matf ter. For instance, an addition of dextrine equaling in weight twenty per cent. of the gelatin or an additionof sugar equaling in` weight, say, tenl per cent. of the gelatin, will be found advantageous. A satisfactory basis can be made by spreading three or four coats of a solution of gum-arabic upon sheets of demyprinting-paper, twenty pounds to the ream, and rolling the surface of the sheets to smooth them when the gum-arabic has dried.

Upon onev of the hereinbefore-described etching-grounds supported'by such a basis the design is produced, removal of portions of the ground being eifected by, for instance, impressing uponL it a block or other device having a design in relief upon it. For example, the grounds will be very useful to the letterpress printer, as it will enable himl to obtain from any type-form a plate which when printed from shall produce white lettering on a dark ground'. To prepare an etching-ground forense in etching a plate, a few impressions of the type-form are pulled upon one of the transferable etching-grounds, the type-form being dry-brushed between each impression. Four impressions are'suflicient to remove the desired parts of the ground before it has become dry by evaporation of the solvent. yIf the ground is in a-dry state, the typeform must be heated *to about blood heat, (98 Fah-` renheit,) in which event three impressions will besufficient to remove the desired partsv ofthe ground. The same method applies to other surfaces having characters or designs thereon. After the design is produced in the etching-ground the ground is transferred by being placed face downward and basis upward on the surface which is to be etched by the acid.` A few sheets of damped blotting-paper are laid on the back of the basis and the Whole is then placed in a press and pressed.` When taken out, the moisture from the damped blotting-paper will be found to have penetrated the basis, which can be readily removed,leavingthe manipulated ground firmly adhering to the surface on the plate desired to be etched. The plate is then immersed in 'an acid-bath and etched to a depth corresponding to the strength of acid and deeply enough for printing from in thel ordinary manner.

Any further depth desired can be obtained by subsequent treatment as for ordinary zinc etching.

In the accompanying drawings in section,V

and E indicates the plate to be etched.

' Ordinarily the acidl` acting "through the Vopenings of theetching-ground produces a sunken design by eating into' the surface eX- posedfbelow the openings; but if thedesign is required to be in relief the transferred ground having the design upon it and lying on the plate is washed overwith an acid-resistin g varnish insoluble in any solvent by which the transferred groundcan be dissolved. Shellac varnish, for example, would serve the required purpose. The varnish should be allowed to dry, after which the plate must be slightly warmed and washed over with turpentine, which removes.V the ground, and in doing so the dried varnish, except where the latter is in direct contact with the plate, and where, consequently, there is nointervening ground-that is to say, exceptwhere the lines or characters of the design'occur. Therefore the latter are formed upon thev plate in protective varnish, and all other parts "of 'the plate save these will be bitten or et'chedwhen the etching-acid-is poured onto it,.so` that the design will be left in relief.

The transferable grounds can "be made of many acid-resistin g materials, alone orin coinbination and other than those hereinbefore speciically referred to by way of example, and the basis of these grounds 'can be made of various substances, preferably those of a gelatinous or glutinous nature for the whollysoluble bases and of a gummy, saccharine', glutinous, farinaceous,`or other material of a viscous or pasty nature' or capable of being readily made so `for the other bases, or ce'llulose or fibrous or other bibulous Vsubstances can be impregnated or coated or otherwise charged on the surfacewithany such substance orl with a soluble subst-ance to form a basis for the acid resisting transferable grounds. A further advantage of my invention-is that a design to be etched can be drawn on a piece of ordinary transfer-paper and have'one of my transferable etching-grounds Vsuperposed upon it. The latter being transparent, the

The various processes hereinbefore de- IOO IIO

The process of preparing etching-grounds i which consists in coating a suitable base with a fil-m of acid-resisting material, perforating said material inY accordance with the design to be etched and removing the lm from the base after perforation for transfer to a plate to -be etched, substantially as described.

In witness whereof I have hereto set my lhand in the presence of the two subscribing zo Witnesses. Y

J QHN BAKER.

Witnesses: Y

FRANK H. SoUrHAM,

ERNEST HARPER. 

